JPH01112004A - Hydraulic servo valve - Google Patents

Abstract

PURPOSE:To make it possible to use water as the working fluid by forming static-pressure bearings at both ends of a spool and also forming a passage, which is led from a pump port to a nozzle-back-pressure-chamber via the static- pressure bearings. CONSTITUTION:Static pressure bearings 14L and 14R are formed at both ends of a spool 10, and a pump port P is connected to a nozzle back-pressure- chamber 18 via a passage 17, the static pressure bearings 14L and 14R, a gap C, and a through hole 18a. With this, the spool 10 and a sleeve 2 can be kept in a non-contact state, thereby preventing the wear caused by the contact between the two. Accordingly, both spool 10 and sleeve 2 can be manufactured by using corrosion resisting material such as plastics. Therefore, water can be used as the working fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic servo valve suitable for using water as a working fluid.

[Prior art] Electro-hydraulic servo valves (hereinafter referred to as hydraulic servo valves) convert weak electrical input signals into hydraulic pressure, switch the direction of working fluid, and change its flow rate. Widely used for operations, etc. An example of the prior art of such a hydraulic servo valve will be described with reference to FIGS. 2 and 3.

In FIGS. 2 and 3, pressure oil is supplied from a pump boat P. When, for example, the coil 22R of the torque motor 21 is excited by the electric input signal and the movable shaft 24 moves to the right, and the lower end 20Ra of the flapper 2OR is displaced to the left, the back pressure in the nozzle back pressure chamber 30R increases and the pilot The pressure in the chamber 31R increases. As a result, the spool 32 is displaced to the left, pressure oil is guided from the pump boat P to a hydraulic cylinder (not shown) via the cylinder boat C1, and return oil from the hydraulic cylinder is returned from the cylinder boat C2 to the passage 33.
and returns to the tank (not shown) via tank boat R.

On the other hand, oil flowing out from between the nozzle 34R and the flapper 20R returns from the tank boat R to the tank via a passage 35.

Here, the oil used as the working fluid is highly flammable, so care must be taken when handling it. There is also the problem of environmental pollution due to waste oil.

By the way, hydraulic drive and its control used to be hydraulic machines, which used water as the working fluid. However, when the working fluid is water, the viscosity of the working fluid is low, so there is a lot of leakage from the gap S (Fig. 3) in the sliding part, resulting in poor efficiency.
Furthermore, there is a problem that there is a lot of wear on the sliding parts, and if the machine is made of metal material (particularly iron), it will rust if left unused.

Recently, advances in new materials such as plastics have been remarkable, and the problem of rust mentioned above, which is one of the problems when using water as a working fluid, can be solved by forming at least the parts of the machine that come into contact with the working fluid with new materials. It can be solved by However, the problem of wear due to the low viscosity of the working fluid still exists, and it is difficult with new materials to machine the sliding parts with high precision to suppress leakage.

[Object of the Invention] The present invention was proposed in view of the problems of the prior art described above.
The purpose is to provide a hydraulic servo valve that solves problems such as rust and leakage.

[Structure of the Invention] The hydraulic servo valve of the present invention includes a spool that is displaced within the valve body to switch the direction of working fluid and change the flow rate, and a nozzle back pressure chamber to which pilot pressure for displacing the spool is applied. , a servo valve equipped with a nozzle and a flapper mechanism consisting of a flapper, wherein static pressure bearings are formed at both ends of the spool, and a passage for working fluid from the pump boat to the nozzle back pressure chamber via the static pressure bearings. has been established.

[Operations and Effects of the Invention] According to the hydraulic servo valve of the present invention, the spool and the valve body can be kept in a non-contact state and wear can be eliminated by the static pressure bearings formed at both ends of the spool. Machining accuracy at the sliding portion with the valve body can be lowered. As a result, the valve body can be manufactured from a new material (for example, plastic) that is difficult to precisely process, and as a result, rust can be prevented even if the working fluid is water. Furthermore, in the prior art, the fluid that is led from the main flow path to the nozzle back pressure chamber and then returned to the tank for use in controlling the nozzle back pressure is not used for purposes other than controlling the nozzle back pressure. In the present invention,
Such working fluids are used as working fluids in hydrostatic bearings before being used in nozzle backpressure techniques. By doing this, part of the leakage of the working fluid can be used effectively.

Furthermore, if water is used as the working fluid in the present invention, the working fluid will be flammable and therefore easy to handle. And even if the working fluid is exhausted, it will not cause environmental damage.

[Preferred Embodiment] When carrying out the present invention, it is preferable to use a non-rusting material such as plastic in the portion that comes into contact with the working fluid. By doing so, rust caused by water can be prevented as described above.

[Example] The present invention will be described in detail below with reference to the drawings.

In FIG. 1, a sleeve 2 is formed on a valve body 1;
A spool 10 is built into the sleeve 2, and both of them are made of rust-resistant material such as plastic material.

A sleeve boat 3 is formed in the sleeve 2, and sleeve ports 4L and 4R are formed on both sides of the sleeve boat 3. The sleeve boat 3 is communicated with a pump boat P, the sleeve boat 4L is communicated with a tank boat R of a water tank (not shown), and the sleeve boat 4R is communicated with the tank boat R via a passage 5. And sleeve boat 3 and sleep boat of sleeve 2) 4L
The intermediate point between the sleeve boat 3 and the sleeve boat 4R is communicated with the cylinder boat C1, and the intermediate point between the sleeve boat 3 and the sleeve boat 4R is communicated with the cylinder boat C2. It communicates with chambers 7L and 7R formed on both sides of the sleeve 2. These chambers 7L and 7R are communicated with chamber 8. Here that room 8
is defined by a cover 1a at the upper part of the valve body 1.

Further, the chambers 7L and 7R are communicated with the gap C via the double tubular gaps 9L and 9R.

A gap C is formed between the spool 10 and the sleeve 2, and in the middle of the spool 10, sleeve boats 3 and 4L of the sleeve 2, sleeve boats 3 and 4
Small diameter portions 11L and IIR having a longitudinal dimension slightly shorter than the spacing between the sleeve 2 and the sleeve 2 are formed, and small diameter portions 12L and 1IR are formed at both ends of the sleeve 2 to fit into the double tubular gaps 9L and 9R.
2R is formed. Then, at both ends of the spool 10, the sleeve 2 and the end face of the spool 10, and the small diameter part 1
Pilot chambers 13L and 13R are formed by 2L and 12R. Further, known hydrostatic bearings 14L and 14R are formed at both ends of the spool 10. Hydrostatic bearing 14
To explain R, the hydrostatic bearing consists of a pocket 15 and a plurality of (four in the illustrated example) orifices 16 arranged at equal intervals in the circumferential direction.
It is communicated with the sleeve boat 3 via 7. Also,
To explain the small diameter portion 12R, the small diameter portion 12R includes a through hole 18a perpendicular to the axis of the spool 10, and a through hole 18a.
A nozzle back pressure chamber 18 communicating with the nozzle back pressure chamber 18 and a nozzle 19 communicating with the nozzle back pressure chamber 18 are provided. Therefore, the pump boat P has a passage 17, a hydrostatic bearing 14R1, a clearance C
It communicates with the nozzle back pressure chamber 18 through the through hole 18a, and further communicates with the chamber 8 through the nozzle 19.

A gap is formed between the nozzle 19 and the flapper 20.
R (The member on the right side in Figure 1: The member on the left side is the flapper 20L.
) are arranged to face each other, and the flapper 2OR is pivotally supported on the valve body 1.

At the center of the chamber 8 described above, a torque motor, generally designated by the reference numeral 21, is provided. The torque motor 21 includes coils 22L, 22R, an armature 23, and a movable shaft 24, and both ends of the movable shaft 24 are connected to the upper ends of the flappers 20L, 2OR. And flapper 2OL, 2
A return spring 25.25 is stretched between the upper end of 0R and the valve body 1.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

Pressure liquid (water) passes through the passage 17 from the pump boat P, and leaks into the gap C from the orifice 16 and pocket 15 of the right hydrostatic bearing 14R, for example, to support the spool 10 in a non-contact manner. The pressure liquid is distributed from the pocket 15 to both sides in the longitudinal direction, and the distribution of the pressure liquid can be determined by the size and length of the gap C and the size of the pocket 15.

The spool 10 is supported without contacting the sleeve 2 by the pressure fluid leaking from the gap C, thereby eliminating wear on both. Therefore, the spool 1 made of plastic material
0 and sleeve 2 can be lowered,
Also, since it is made of plastic material, it can prevent rust.

The pressure liquid flowing to the right in the axial direction through the gap C flows into the pilot chamber 13.
From R, it passes through the nozzle back pressure chamber 18 and the nozzle 19 and flows out from the gap. The outflowing water is returned to the tank via the chamber 7L1 passage 6, the sleeve port 4R1 passage 5, and the tank boat R.

In operation, when, for example, the coil 22R of the torque motor 21 is excited by an electric input signal, the movable shaft 24 moves to the right, and the end 2°Ra of the flapper 20R is displaced to the left.
The back pressure in the nozzle back pressure chamber 18 increases. As a result, the pressure in the pilot chamber 13R increases and the spool 10 is displaced to the left. Therefore, the pressure liquid is transferred from the pump boat P to the sleeve boat 3.
, are led to a hydraulic cylinder (not shown) via a cylinder boat C2. The return pressure liquid from the hydraulic (hydraulic) cylinder is from the cylinder boat C1 to the sleeve boat 4L.

It is returned to the tank via tank boat R. coil 22
When L is energized, the operation is opposite to that described above.

[Summary] As explained above, according to the present invention, the leakage flow is actively used to form a static pressure bearing, the spool and sleeve are maintained in a non-contact state to prevent wear of both, and By appropriately designing the bearing characteristics, the size of the sleeve can be set arbitrarily, making it possible to lower the machining accuracy. Therefore, the spool and sleeve can be manufactured using a rust-resistant material such as a plastic material, and rust can be prevented. Therefore, water can be used as the working fluid.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are configuration diagrams each showing a prior art. 1...Valve body 2...Sleeve 6.17...
・Aisle 10...Spool 13L, 13R...
・Pilot chamber 14L, 14R...Static pressure bearing
16... Orifice 18... Nozzle back pressure chamber 19
...Nozzles 20L, 20R...Flapper 21.
...Torque motor diagram 3

Claims (1)

[Claims] A servo equipped with a spool that is displaced within the valve body to switch the direction of working fluid and change the flow rate, a nozzle back pressure chamber to which pilot pressure is applied to displace the spool, and a flapper mechanism consisting of a nozzle and a flapper. A hydraulic servo valve, characterized in that static pressure bearings are formed at both ends of the spool, and a working fluid passage is provided from the pump port to the nozzle back pressure chamber via the static pressure bearings.